Our colleagues at the National Metrological Institute of Japan, Igor Maksimov and Toshiaki Asakai, have completed a set of Harned Cell measurements of HCl activities in HCl/TrisHCl solutions at different concentrations and temperatures. These data will be used to develop the chemical speciation model of Tris (2-Amino-2-hydroxymethyl-propane-1,3-diol, or THAM) buffers in seawater.They are the first of many sets of similar measurements that will be made in solutions containing Tris, TrisH+, Cl- and the inorganic components of seawater.
We are pleased to announce that Matthew Humphreys, currently working at the National Oceangraphy Centre in Southhampton, will be joining Simon Clegg at UEA. He has been appointed to a 3 year postdoc position to work on the development of the chemical speciation model. He starts work on 1 November 2017.
Matthew is a chemical oceanographer, and his field of study is the marine carbonate system. He did his Ph.D with WG 145 associate member Eric Achterberg.
Matthew’s position is supported by a grant from the Natural Environment Research Council of the UK, which is part of the UK/USA collaboration with WG 145 member Andrew Dickson (whose contribution is supported by the US National Science Foundation).
Simon Clegg has just completed a visit of two and a half months to the University of Gothenburg, Sweden, where he worked with WG 145 Chair David Turner. Experimental work needed for the development of the chemical speciation model was planned, and the current “state of the science” Pitzer model of artificial seawater was assembled and the parameters checked. Our initial goal is to develop a metrologically traceable model of Tris/TrisH+ buffers in artificial seawaters, as a function of both salintiy and temperature. The planned experiments reflect this, and include solutions such as Tris/TrisH+ in NaCl(aq), H+/TrisH+/Cl- solutions, and Tris/TrisH+ in aqueous NaCl/Na2SO4, for example.
The large experimental effort will be shared between Andrew Dickson at Scripps Institution of Oceanography, and our colleagues at the national metrological institutes of Germany, France, and Japan, and at GEOMAR in Kiel (Germany).
We have recently learned of two new/recent projects that, while entirely independent of
our research, are closely related:
- Robert (Bob) Byrne at the University of South Florida, has a three year project entitled “Development of Spectrophotometric pH Measurement Capabilities in Estuaries” (supported by NSF).
- Wei-Jun Cai at the University of Delaware has been funded by NOAA to work on improving scientists’ ability to measure pH in dilute seawater (estuarine environments), and to evaluate the behaviour of different types of electrode. He will be collaborating with scientists at the National Institute of Standards and Technology.
We look forward to exchanging information (and collaborating, if possible) with both Bob and Wei-Jun, beginning with a web-based conference in December 2017.
Following the success of WG 145 members Simon Clegg, Heather Benway, and Andrew Dickson in obtaining 3 year grants from NERC (in the UK) and NSF in the USA, we are very pleased to announce major additions to our collaboration:
- Frank Bastkowski and Steffen Seitz, of Physikalisch-Technische Bundesanstalt (PTB), Braunschweig.
- Igor Maksimov and Toshiaki Asakai, of the National Metrology Institute of Japan.
- Daniela Stoica, of the Laboratoire national de métrologie et d’essai, Paris.
- Pablo Lodeiro and Eric Achterberg, of GEOMAR (the Helmholtz Institute of Ocean Research, Kiel).
The first three groups will all be making Harned Cell measurements of HCl activities in solutions containing Tris/TrisH+ buffer, and the components of seawater (beginning with NaCl).
Pablo and Eric will be measuring salt solubilities in aqueous mixtures, to obtain values of the activities of the salts at saturation. They may also be carrying out potentiometric titrations.
The purpose of both types of experiments is to obtain the activities of dissolved species in the solutions, and so determine the parameters of the Pitzer the chemical speciation model we are developing. These parameters, whose values are functions of temperature and pressure, express the strength of interactions between pairs of cations and anions, and then triplets of ions (two ions of one sign, and one ion of opposite sign). They can only be determined by fitting to measurements.
We and proud to announce that the Natural Environment Environment Council of the UK, and the National Science Foundation in the USA, have awarded a 3 year grant to the project “NSFGEO-NERC: A Thermodynamic Chemical Speciation Model for the Oceans, Seas, and Estuaries“. The investigators on this project are WG members Simon Clegg (University of East Anglia), Andrew Dickson (Scripps Institution of Oceanography), and Heather Benway (Woods Hole Oceanographic Institution).
Model development will be carried out at UEA, and experiments (using Harned Cells and a calorimeter) at Scripps. Heather, who is the Executive Officer of NSF’s Ocean Carbon and Biogeochemistry programme, is our link to the chemical oceanography community and will ensure that our efforts meet their needs.
Our Working Group is dedicated to advancing the ability of chemical oceanographers to model chemical speciation in seawater and other natural waters. We are collaborating with a group of national metrological institutes to carry out new laboratory measurements to characterise the thermodynamic properties and speciation in the major and minor components of seawater, and in the aqueous buffers used to calibrate instruments for measuring pH. Concurrently, we are also working on an uncertainty analysis of currently available data and “Pitzer” speciation models.
The aim of the Working Group is, over a period of years, to develop a user-friendly comprehensive chemical speciation model of seawater and related natural waters. The model will include a full treatment of uncertainties. Our efforts are supported by grants from the Natural Environment Research Council in the UK, and the National Science Foundation in the USA. This Working Group is sponsored by the Scientific Committee on Oceanic Research.
On this website we describe our activities and achievements, and current activities of interest to the chemical oceanography community. For further information, please contact either David Turner (firstname.lastname@example.org), or Simon Clegg (email@example.com).